Top-aligned beamer frame: remove "automatic paragraph"

Question

Update

There is already a solution in @mickep's comment, which is \noindent. I am waiting for an answer from them that I can accept or I will soon write one myself that contains their solution. Thank you all!

Original post

In our insitute's Beamer template, top-aligned frames are preferred. When I start the frame with an equation, there is space left for one line of text, which I can only remove using \vspace*{-SomeSpace}. Is there a frame or class option that prevents the inclusion of this empty line of text? Thanks.

MWE:

\documentclass[t]{beamer}

\begin{document}

\begin{frame}{Frametitle 1}
\begin{equation*}
    aa = bb
\end{equation*}
\end{frame}

\begin{frame}{Frametitle 2}
Hey, here is some text.
\begin{equation*}
    aa = bb
\end{equation*}
\end{frame}

\end{document}

If you move back and forth between the two slides in presentation mode of your PDF viewer, you see that there is space for some phantom text on the first slide.

Answer 1

The solution will not be found within beamer.

The equation* is defined by amsmath and the space above can be controlled redefining \abovedisplayshortskip , which is used when the line above is "short".

Of course, this will apply to all equation environments.

\documentclass[t]{beamer}

%****************** added <<<<<<<<<<
\usepackage{xpatch}
\xapptocmd{\normalsize}{\abovedisplayshortskip=-\the\baselineskip}{}{}
%*******************************

\begin{document}
    
    \begin{frame}{Frametitle 1}
        \begin{equation*}
            aa = bb
        \end{equation*}
    \end{frame}
    
    \begin{frame}{Frametitle 2}
        Hey, here is some text. 
        
        \begin{equation*}
            aa = bb
        \end{equation*}
    \end{frame}
    
\end{document}

For the meaning of "short" see abovedisplayskip vs abovedisplayshortskip

Answer 2

I will add @mickep's comment (below the original post) as an answer because I find it the best.

I have not tested, but it sounds like indentation. Does \noindent help?

The solution is to add \noindent to the beginning of the slide that should start with an equation.

Updated MWE from the OP:

\documentclass[t]{beamer}

\begin{document}

\begin{frame}{Frametitle 1}
\noindent
\begin{equation*}
    aa = bb
\end{equation*}
\end{frame}

\begin{frame}{Frametitle 2}
Hey, here is some text.
\begin{equation*}
    aa = bb
\end{equation*}
\end{frame}

\end{document}

@SimonDispa's answer and @Sebastiano's answer also work but are not as nice as @mickep's in my opinion.

Answer 3

When I start the frame with an equation, there is space left for one line of text ... Is there a frame or class option that prevents the inclusion of this empty line of text?

Seriously, what do you think you're accomplishing -- in terms of providing reasonably digestible information to the audience of your beamer-based talk -- if you start the contents of a frame with a displayed equation? Do you maybe secretly detest the audience?

I'm afraid I know of no class or frame option that accomplishes your formatting objective. A non-kludgy hands-on way to accomplish your objective is to encase the contents of the frame in a minipage environment. E.g., you could replace

\documentclass[t]{beamer}
\begin{document}
\begin{frame}{Frametitle 1}
\begin{equation*}
    aa = bb
\end{equation*}
\end{frame}

with

\documentclass[t]{beamer}
\begin{document}
\begin{frame}{Frametitle 1}
\begin{minipage}{\textwidth}
\begin{equation*}
    aa = bb
\end{equation*}
\end{minipage}
\end{frame}

---

\documentclass[t]{beamer}

\begin{document}
\begin{frame}{Frametitle 1 -- no embedded minipage}
\begin{equation*}
    aa = bb
\end{equation*}
\end{frame}

\begin{frame}{Frametitle 2 -- with embedded minipage}
\begin{minipage}{\textwidth}
\begin{equation*}
    aa = bb
\end{equation*}
\end{minipage}
\end{frame}

\end{document}